Chadbourne & Parke and Pillsbury Winthrop Shaw Pittman have called off merger talks following months of speculation, The Lawyer understands.

Had the merger gone forward, it would have created US powerhouse with 930 lawyers and turnover above $800m (£526.3m).

The talks, called off after two months of speculation, followed the news that Pillsbury called a mandatory partner meeting to put the merger to a vote.

It was thought that a merger between the two firms would expand the firm’s headcount in key practice areas such as financial services and energy.

Pillsbury’s CEO of nine years Jim Rishwain has engaged in merger talks with at least six firms, including legacy Fulbright & Jaworski and Orrick Herrington & Sutcliffe, during his time at the helm, but none have proved successful.

Sources say that the firm’s 1:1 partner associate ratio has been one of the main causes for the lack of merger success. 

Rishwain is set to step down from his role in January 2017, with Washington DC litigator David Dekker set to take on his role after being announced as the firm’s new vice-chair and chair elect earlier this year. 

In January Rishwain announced his intention to double the headcount of the firm’s 13-partner London office. The hires will expand Pillsbury’s financial services, energy, technology and real estate practices.

Pillsbury chair Jim Rishwain declined to comment.

Chadbourne did not return requests for comment.